First differences of the central trinomial coefficients A002426.

Terms

a(0) =0a(1) =2a(2) =4a(3) =12a(4) =32a(5) =90a(6) =252a(7) =714a(8) =2032a(9) =5814a(10) =16700a(11) =48136a(12) =139152a(13) =403286a(14) =1171380a(15) =3409020a(16) =9938304a(17) =29017878a(18) =84844044a(19) =248382516a(20) =727971360a(21) =2135784798a(22) =6272092596a(23) =18435108258a(24) =54228499920a(25) =159636389850a(26) =470256930052